[en] HIF-1 is the main transcription factor responsible for increased gene expression in hypoxia: VEGF, erythropoietin, GLUT-1, and glycolytic enzymes are such target genes and all participate in the adaptative response of cells to hypoxia. AP-1 activation by hypoxia has also been demonstrated in several cell lines and it cooperates with HIF-1 for increasing VEGF gene transcription in hypoxia. Both HIF-1 and AP-1 activation by hypoxia seems to involve members of the MAP kinase family. Here, we summarize the data indicating that ERK and JNK are needed for activation of HIF-1 and AP-1, respectively.